The photo-electrochemical study of the hetero-junction Ag/NiO (5/95 wt%) prepared in situ by nitrate route was investigated to assess its photoactivity for the hydrogen production upon visible light. The X-ray diffraction pattern shows narrow peaks of Ag and NiO. The direct optical gap of the sensitizer NiO (1.51 eV) is well matched to the solar spectrum. It acts as n-type semiconductor and the potential of its conduction band (- 0.35 V-SCE), determined from the capacitance measurement, is more negative than the H2O/H-2 level (similar to - 0.3 V-SCE), yielding water reduction under visible light; the photoactivity peaks at pH similar to 13. The excited electrons are transferred to Ag clusters, to reduce water into gaseous hydrogen owing to the low H-2-over-voltage (similar to 160 mu mol). A quantum conversion efficiency of 0.11% is reported under visible light (3.42 x 10(18) photons s(-1)) within similar to 10 min with an evolution rate of 96 mu mol h(-1) mg(-1). The catalyst was tested for several successive photocatalytic cycles, a deactivation effect of similar to 7% per cycle is observed, thus proving its stability and repeatability. The heating of the catalyst under dynamic vacuum at 250 degrees C restores the initial photoactivity.